Method for winding of filaments

ABSTRACT

The invention relates to a method for winding pre-oriented, non-crystalline polyester filaments onto a spool at a winding speed of at least 4,200 m/min, in which the wound filament is wound over the width of the spool by means of a flying traverse arm and is turned by a driven sensing roller with an applied pressure between 8 and 18 kg on the circumference of a spool placed on a driven spool-locating pin. The filaments for winding are introduced to the traverse thread guide at a thread tension of between 0.03 cN/dtex and 0.20 cN/dtex. The sensing roller is driven at an overspeed of preferably between 0.3 and 1.2%, in comparison with the spool circumferential speed. The thread laying angle is set between 3.5° and 7.5° by means of the spool travel. The above method permits a good spool formation even at high spooling speeds.

The present invention relates to a process for winding up filaments toform a package at high winding speeds. Specifically the inventionrelates to a process for winding up POY polyester filaments.

The yarn package is the most important form of storing, processing orshipping yarn. Yarn packages have to meet high requirements. Moreparticularly, the yarn package should not affect the yarn's propertiesand should have good unwinding properties.

A good package build requires high precision of the package surfacespeed. Various ways of driving the package are known. In spindle drive,the spindle holding the package is driven and its surface speed isvaried. As the package diameter increases, the rotational speed of thespindle decreases. It is known to measure the surface speed using afeeler roll which rests against the surface of the package. As thepackage diameter increases over the winding time of the yarn, thesurface speed increases. This increase is transmitted to the rotationalspeed of the feeler roll. A control signal is generated to reduce therotational speed of the spindle as the package diameter increases. Inthe case of friction drive, a presser roll resting against the surfaceof the package drives the undriven spindle at a constant surface speed.

There are also spindle-drive winding machines where the feeler orfriction roll is likewise equipped with a motor drive for the purpose ofmeasuring the surface speed. This makes available an additional variablewhich is known as the gain of the feeler roll compared with the package.

A positive gain generates a command signal to the drive of the feelerroll to increase the speed, and a negative gain generates a signal toreduce speed. In either case, the feeler roll remains in contact withthe package, so that the feeler roll exerts either an accelerating or adecelerating effect on the package. In the case of Bamag's CW winder,the gain is set by means of a load displacement factor, which is definedin scale divisions. A positive gain is set using a positive loaddisplacement factor with the scale value approximately characterizingper mill (‰) units of the gain.

Various traversing systems are known for placing the yarn across thewidth of the package to be wound. There are yarn guides which moveforward and backward and whose direction of movement is abruptlyreversed at the package edge, and this leads to appreciable accelerationforces and can contribute to very rapid wear. Rotating propellersystems, in contrast, move the yarns forward and backward substantiallymore quickly, but the yarn may be exposed to a shocklike stress at thepoint where it reverses direction.

Polyester POY filaments are customarily produced at takeoff speeds of 2500-3 500 m/min, depending on the linear density to be produced. Suchfilaments have breaking extension values of 75-165%, which have provedadvantageous for further processing in a drawing or draw-texturingoperation.

However, on increasing the winding speed, akin to the production ofspin-oriented, crystalline FOY or HOY PET filaments, there areincreasing defects, which induce process and quality upsets when thefilaments are unwound from the packages for the purpose of furtherprocessing.

The production of POY yarns at high winding speed is described forexample in the following references:

WO 99/51799 discloses a process for spinning continuous filaments bycooling the freshly spun filaments in a tube using an acceleratedcooling gas. This makes it possible to raise the spinning takeoff speedto 4 530 m/min without reducing the breaking extension of the filaments.

WO 99/07927 describes a process for producing POY filaments frompolyester-based polymer blends. PES filaments having high breakingextension values are obtained in the presence of a certain amount of anadditive copolymer even at high spinning takeoff speeds of up to 6 000m/min.

Although the cited processes make it possible to spin POY filaments athigh takeoff speeds, the winding up of the filaments and the avoidanceof package defects has not been further described.

It has been found in commercial practice that filaments produced at highspinning takeoff speeds can give rise to the following defects inwindup:

-   -   The high centrifugal forces due to the rotating package are        responsible for an uncontrolled collapse of the package when the        full package is braked.    -   High friction forces between the surface of the package and the        feeler roll lead to flexing and to a buildup of heat.    -   Especially bellying at the package flanks, saddle formation        across the width of the package and dropped ends. These defects        can arise or worsen even during the storage of the POY packages.    -   In this context, it must be borne in mind that the spinning        takeoff speed is defined by the speed of the first takeoff        element, usually a godet, and the winding speed corresponds to        the surface speed of the package.

The literature identifies the most frequent causes for defective packagebuild as being a wrong wind per double traverse and a wrong windingtension onto the package. Increasing excessive winding tension willinitially cause the yarn to build up at the ends, so that the packageforms a saddle in the middle, and will then cause dropped ends andbroken ends. Insufficient yarn tension will initially give rise to aribbony surface, associated with bulging package ends, an increasingnumber of dropped ends and, in the event of even greater yarnoverfeeding, loop formation, broken ends and wraps on the friction roll(Franz Fourné, Synthetische Fasern, Carl Hanser Verlag Munich Vienna,1995, pages 210 ff.).

A winding machine with a driven contact roll and a driven package holderis known from JP 63-147 780 A. A winding method for highly crystallineyarns is described. But the stated winding parameters are not applicableto noncrystalline yarns. Besides, the angle of wind is not specified.The setting of an identical speed for the package surface and thecontact roll means that dropped coils at the ends of the package areunavoidable.

JP 62-244873 A likewise describes a winding machine with contact rolland package holder which are driven. Here too the focus is on thewinding of highly crystalline yarns. Therefore, there is again arequirement for agreement between the speeds of the contact roll and ofthe package surface. Dropped ends are likewise unavoidable.

JP 11-263534 A concerns the winding up of acrylic fiber. But the changein the winding tension as the package builds up is not acceptable forPES yarns.

It is an object of the present invention to provide a process forwinding up POY polyester filaments whereby good package build can beobtained even at high winding speeds. The process shall further providea package build to provide high yarn weights on the package of more than4 kg, preferably 12-32 kg, and good package unwinding process at furtherprocessing even after prolonged storage of the package.

This object is achieved according to the invention by the featuresindicated in claim 1. Advantageous modifications of the processaccording to the invention form the subject matter of subclaims.

It has been determined that, surprisingly, good package build isobtainable in the case of POY polyester filaments even at high windingspeeds on

-   -   feeding the filaments to be wound up to the traversing filament        guide at a yarn tension between 0.03 cN/dtex and 0.20 cN/dtex,    -   operating the feeler roll at a positive gain compared with the        package surface speed,    -   setting the angle of wind to be between 3.5° and 7.5° throughout        the package, and    -   setting the contact force of the feeler roll on the package        surface between 8 and 18 kg.

Yarn refers to the bundled multifilaments. POY filaments are inparticular filaments having a breaking extension between 75 and 165%.All polyesters can be used, for example PET, PBT, PTT or the like.

The winding tension in cN/dtex at which the filaments to be wound up arefed to the traversing yarn guide is determined by forming the quotientof the yarn tension in cN measured directly above the traversing yarnguide and the linear density in dtex of the wound-up yarn. The processof the invention does not absolutely presuppose the use of godets. Whenthe filaments are taken off using godets, the yarn tension which ismeasured is the yarn tension of the filaments fed by the last takeoffgodet to the traversing yarn guide. The yarn is laid over the traverselength by means of rotating propellers.

The setting of the mandated force with which the feeler roll pressesagainst the surface of the package ensures a frictional connectionbetween the package and the roll.

Angle of wind refers to the angle between the yarn direction on thepackage and the perpendicular to the axis of rotation of the package. Anangle of wind between 3.5° and 7.5° throughout the package contributesto stabilizing the package build.

Owing to the positive gain at which the feeler roll is operated comparedwith the package surface speed, the feeler roll exerts an acceleratingeffect on the package. It has been determined that, surprisingly, theaccelerating effect has a substantial influence on the avoidance ofdropped coils especially when POY is produced at high winding speeds.

Setting the angle of wind within the abovementioned limits contributesto the fact that the package is devoid of saddle formation and bellying.

Particularly good package build is obtained when the feeler roll isoperated at a positive gain of between +0.3 and +1.2% compared with thepackage surface speed. The traversing yarn guide is preferably fed withthe filaments at a yarn tension between 0.05 cN/dtex and 0.15 cN/dtex.

To further improve package build, the angle of wind of the filaments ispreferably varied throughout the package as a function of the packagediameter. Varying the angle of wind is a way of imposing furtherlimitations on transportation damage and unwinding defects due tobellying. It is particularly advantageous for the angle of wind in afirst phase to increase with increasing package diameter and in asubsequent, second phase to decrease with increasing package diameterthroughout the package. The angle of wind preferably increases anddecreases incrementally in approximately 0.5° steps. Between the firstand second phases, the angle of wind is preferably kept constant.

In the context of the present invention, the PES may also comprise asmall fraction, preferably up to 0.1% by weight, based on the totalweight of the filament, of brancher components. Preferred branchercomponents according to the invention include polyfunctional acids, suchas trimellitic acid or pyromellitic acid, or tri- to hexavalentalcohols, such as trimethylolpropane, pentaerythritol,dipentaerythritol, glycerol or corresponding hydroxyacids.

In may further be advantageous to admix the PES with up to 2.5% byweight, based on the total weight of the filament, of additive polymersas extensibility enhancers. Particularly useful additive polymersaccording to the invention include polymers and/or copolymers. Thedisclosure content of DE 10063286 is incorporated herein in this respectby reference.

The process according to the invention can in principle utilize allcustomary winding machines whereby the parameters mentioned can be set.It is advantageous for the process of the invention to use aspinning-cooling means which reduces stress-induced crystallization athigh spinning takeoff speeds. A particularly preferred embodiment of thepresent invention utilizes a spinning-cooling means as described in WO99/51799. The disclosure of this reference is explicitly incorporatedherein in this context by reference.

The filaments may be entangled in a conventional manner before beingwound up. Any entangling is preferably done to node counts of at least10 n/m (measured on the wound-up yarn).

For the yarn tension to be set according to the invention, the windingspeed of the POY polyester filaments should be 0 to 2% below the packagetakeoff speed. When the filaments are taken off using godets, thetakeoff speed refers to the circumferential speed of the first godetunit.

It is further advantageous to employ a pattern-breaking mechanism inorder that trapped yarn coils may be avoided in the extreme packagepositions specifically.

The process of the invention will now be more particularly describedwith reference to the drawings, in which

FIG. 1 shows a greatly simplified diagrammatic depiction of a windingmachine for use in the process of the invention and

FIG. 2 shows the variation in the angle of wind throughout the package.

In the process of the invention, a melt of the polyester or polymerblend is pumped by spinning pumps into spinneret packs to be extrudedthrough the holes in the die plate of the pack to form molten filaments.The extruded filaments pass through a quench delay zone. A reheater canbe disposed below the spinning beam. The filaments are subsequentlycooled to temperatures below the solidification temperature.

Means for cooling filaments are known from the prior art. The filamentsmay be cooled using for example single end systems comprising singlecooling tubes having a perforated wall. Cooling of each individualfilament is obtained through active cooling air supply by utilizing theself-suction effect of the filaments and/or through aspiration of thecooling air. As an alternative to the individual tubes, it is alsopossible to use the familiar crossflow quench systems.

The bundling of the filaments to form at least one end takes place in anoiler pin which supplies the yarn with the desired amount of spin finishat a uniform rate. Before being wound up, the filaments of the yarn maybe entangled to improve bundle coherency on the package.

The winding machine for winding up the continuously arriving yarncomprises a motor-driven package mandrel 1 onto which the package orbobbin former 2 has been pushed. It is on the package former 2 that theyarn 3, continuously arriving at a constant speed, is wound to form apackage 4.

The yarn 3 initially passes through a yarn guide 5, which forms the tipof the traversing triangle. The yarn then arrives at a traversing means6. The winding machine preferably possesses a propeller wheel traversemotion (depicted only in outline) which comprises a traverse drive 7 andtwo counterrotating propeller systems 8, 9 per yarn. Such a rotor typeyarn laying system forms part of the prior art and is described forexample in Fourné, Synthetische Fasern, Carl Hansa Verlag Munich Vienna,1995, page 401.

The propellers 8, 9 of the rotor type traversing system move the yarn 3back and forth over the traverse length. The yarn tension at which thearriving filaments are fed to the traversing yarn guide is between 0.03cN/dtex and 0.20 cN/dtex and preferably in the range from 0.05 cN/dtexand 0.15 cN/dtex. The magnitude of the frequency of the traversing means6 is varied to set an angle of wind for the yarn of between 3.5 and 7.5°throughout the package.

Below the traversing means 6, the yarn is redirected by more than 90° ata feeler roll 10 and then wound up on the package former 2 to form thepackage 4. The feeler roll 10 has a separate drive. The directions ofrotation of the package mandrel 1 and of the feeler roll 10 are eachidentified by arrows. The contact force F of the feeler roll bearingagainst the surface of the package can be varied on the winding machine.The contact force F is set between 8 and 18 kilograms.

The rotational speed of the package mandrel 1 is varied so that thepackage surface speed is constant. Irrespective of the variation of thepackage mandrel, the drive of the feeler roll 10 is set to positivegain, so that it exerts an accelerating effect on the package. Thispositive gain between feeler roll drive compared with package mandreldrive is preferably between +0.3 and +1.2%.

The angle of wind is varied within the limits of 3.5° and 7.5°throughout the package. FIG. 2 shows the angle of wind (°) as a functionof the package diameter (%) relative to the full package (100%). At thestart, the angle of wind is preferably set to 4.5°. In a first phase Iup to a relative package diameter of 40%, the angle of wind isincrementally increased from 4.5° to 6°. Subsequently, the angle of windremains constant within this range up to a relative package diameter of60%. This is followed by a second phase II, in which the angle of windis incrementally decreased from 6.0° to 5.5°. The upper and lower limitsbetween which the angle of wind should be set throughout the package areshown as broken lines in FIG. 1. The upper and lower limits are each1.0° above and below, respectively, the particularly preferred values.

Other winding machines differ in their geometry, the hardware and theprocess control system. The winder conditions of the invention providestable, defect-free packages. The filaments are formed into packages ata winding speed of at least 4 200 m/min, preferably ≧4 600 m/min andespecially ≧6 000 m/min. A range which is particularly preferred in thecontext of the invention is that between 4 200 and 8 000 m/min andespecially between 4 600 and 7 000 m/min.

1. A process for winding up POY polyester filaments to form a package atwinding speeds of at least 4,200 m/min by the arriving filaments beingfed to a traversing yarn guide, being laid over the traverse length ofthe package and being redirected by a driven feeler roll which bearswith a mandated contact force against the surface of the package whichsits on a driven mandrel, wherein it comprises feeding the filaments tobe wound up to the traversing filament guide at a relatively high yarntension between 0.03 cN/dtex and 0.20 cN/dtex, operating the feeler rollat a higher surface speed than the package surface speed, setting theangle of wind between 3.50 and 7.50 degrees throughout the package, andsetting the contact force of the feeler roll between 8 kg and 18 kg. 2.The process as claimed in claim 1, wherein the feeler roll (press roll)is operated at a positive gain of between 0.3% and 1.2% for its surfacespeed compared with the package surface speed.
 3. The process as claimedin claim 1, wherein the filaments are fed to the traversing yarn guideat a tension of 0.05 cN/dtex to 0.15 cN/dtex.
 4. The process as claimedin claim 1, wherein the angle of wind of the filaments is variedthroughout the package as a function of the package diameter.
 5. Theprocess as claimed in claim 4, wherein the angle of wind in a firstphase increases with increasing package diameter and in a subsequent,second phase decreases with increasing package diameter throughout thepackage.
 6. The process as claimed in claim 5, wherein the angle of windis kept constant between the first and second phases.
 7. The process asclaimed in claim 1, wherein the traversing yarn guide is fed with anentangled yarn having at least 10 nodes/m.
 8. The process as claimed inclaim 1, wherein the filaments are wound up at a speed between 4,600 and7,000 m/min.
 9. The process as claimed in claim 1, wherein the arrivingfilaments are laid down by means of rotating propeller systems.
 10. Theprocess as claimed in claim 7 wherein the filaments are wound up at aspeed between 4,600 and 7,000 m/min.